Self adjusting rate responsive cardiac pacemaker and method

• US 4,884,576 A
• Filed: 09/28/1988
• Issued: 12/05/1989
• Est. Priority Date: 09/28/1987
• Status: Expired due to Term

• Current Assignee: Eckhard Alt
• Original Assignee: Eckhard Alt
• Inventors: Alt, Eckhard
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): GETZOW, SCOTT M
• Application Number:
  US07/250,242
• Time in Patent Office: 433 Days
• Field of Search: 128/419 PG, 128/419 P, 128/736, 128/716, 128/723, 128/734, 128/635, 128/636, 128/637
• US Class Current: 607/18
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36571 controlled by blood flow rate, e.g. blood velocity or cardiac output

Abstract

It has been found from studies of healthy persons and patient'"'"'s wearing pacemakers that the basic cardiovascular condition and the heart rate response to exercise varies considerably between different individuals. Thus, for effective control the individual differences must be taken into account. It would not be desirable to face the complexity of a pacemaker system that did not automatically adjust to these individual differences because there could not be knowledgeable persons in the field who could establish critical control conditions. This invention thus provides pacemaker methods for automatically establishing operating conditions for proper pacing rate control of a wide range of different individual conditions. Thus on line real time physiologically variable signals from the patient indicative of the patient'"'"'s basic condition and suitable for pacing rate control are averaged over long and short term intervals and used to develop a pacing control signal. Typically the respiratory rate signal taken from a patient will provide information for adjusting the pacing rate to both the basic condition of the patient and the instanteous conditions encountered such as exercise.

Claims

1. The method of relating the pacing rate for a patient'"'"'s heartbeat comprising the steps of:

producing in response to activity of the patient at least one on-line real-time signal sensed by monitoring the dynamic activity of the patient,

developing from said signal a long term average indicating the condition of the patient representative of the patient'"'"'s basic cardiopulmonary condition,

establishing a basic base line characteristic relationship to the long term average from said signal as the primary pacing signal for control of the patient'"'"'s heartbeat,

establishing a short term average from the real-time signal representative of the patient'"'"'s instantaneous cardiopulmonary condition,

varying the base line characteristic upward and downward as a function of the short term average to produce a dynamically modified pacing control signal incorporating both said long term average and said short term average, and

pacing the patient'"'"'s heartbeat as a function of the dynamically modified pacing control signal.

2. The method of claim 1 with the further steps of:

deriving from said on-line signal a signal representing a long term average of the patient'"'"'s tidal volume representing his individual basic cardiopulmonary condition as said long term average, and

deriving from said on-line signal a signal representing a short term average of the patient'"'"'s tidal volume as said short term average representing the instantaeous cardiopulmonary condition of the patient. varying the basic tidal volume signal as a function of the short term average of the tidal volume signal to establish a tidal volume control signal, and varying the pacing control signal as a function of the tidal volume control signal.

3. The method of claim 1 with the further steps of:

producing from the cardiovascular system of the patient an on-line real-time cardiac signal representative of the patient'"'"'s cardiac activity,

deriving from the cardiac signal a long term average representing the patient'"'"'s basic cardiac condition as a basic cardiac signal,

deriving from said cardiac signal term average as an instantaneous cardiac signal representing the patient'"'"'s instantaneous cardiac condition,

varying the basic cardiac signal as a function of the instantaneous cardiac signal to derive a cardiac control signal, and

varying the dynamically modified pacing control signal additionally as a function of the cardiac control signal.

4. The method of claim 1 with the further steps of:

producing in response to the physical activity of the patient a further activity signal representative of the level of further physical activity of the patient,

developing a long term average of the further activity signal to produce a basic further activity signal representative of the basic level of physical activity of the patient,

developing a short term average of the further activity signal to produce an instantaneous activity signal representative of the instantaneous further physical activity of the patient,

varying the basic further activity signal as a function of the instantaneous further activity signal to provide a further activity control signal, and

varying the dynamically modified pacing control signal further as a function of the further activity control signal.

5. The method of claim 1 with the further steps of:

producing in response to physical activity of the patient a further activity signal representative of the level of further physical activity of the patient, and

varying the dynamically modified pacing control signal additionally as a function of the further activity signal.

6. The method of controlling the pacing rate of a patient wearing a pacemaker comprising the steps of:

isolating at least one on-line real-time activity signal from the cardiovascular-pulmonary system of a patient representative of a physiological activity variably related to the change of heartbeat rate in a normal person,

developing a base line charteristic from a long term average of said activity signal.,

developing an instantaneous activity signal from a short term average of the activity signal,

varying the base line characteristic upward and downward dynamically to produce a modified long term average as a function of the instantaneous activity signal to produce a pacing control signal, and

pacing the heart at a rate controlled by the pacing control signal.

7. A heart pacemaker comprising in combination, pulse generator means for producing pacing pulses, means for measuring at least one parameter varying with physiological activity of a patient representative of dynamically changing physiological activity and individual characteristics of the patient relating to pacing rate, means responsive to the measured parameter for obtaining and averaging measured data relating to pacing rate over a predetermined long term period and establishing therefrom a base line characteristic, means for modifying the base line characteristic upward and downward dynamically with a short term average of a measured parameter to account for instantaneous dynamic changes for producing a pacing control signal incorporating dynamic changes in pacing rates, and means for controlling the pacing rate of the patient as a function of the dynamically modified base line characteristic of the pacing control signal.

8. The pacemaker of claim 7 wherein said parameter is the respiratory rate of the patient.

9. The pacemaker of claim 7 including means for further modifying the base line characteristic by a sub-signal of a different parameter related to the patient'"'"'s physiological activity.

10. The pacemaker of claim 7 wherein said parameter is related to the pulmonary activity of the patient.

11. The pacemaker of claim 7 wherein said parameter is related to the cardiac activity of the patient.

12. The method of regulating the pacing rate for a patient'"'"'s heartbeat comprising the steps of:

producing from a patient an on-line real-time dynamic physiological activity signal representative of a condition relating to the heartbeat rate,

producing a long term average of said physiological activity signal,

establishing from the long term average a pacing function having a substantially linear relationship with the heartbeat rate with a predetermined slope,

producing a short term upward and downward variation from said pacing function in response to a parameter of the activity signal, and

pacing the patient'"'"'s heart at a rate corresponding to a combination of short term variation and said pacing function thereby to produce a smooth transition in pacing rate when exercise is encountered and terminated.

13. Pacemaker apparatus for regulating the pacing rate of a patient comprising in combination:

sensing means for deriving from the patient an on-line real-line time dynamic physiological activity signal representative of a condition related to the heartbeat rate,

processing means for producing a long term average pacing function of said signal having a sunstantially linear relationship with the heartbeat rate of a predetermined slope,

means for producing a short term upward and downward variation from said pacing function in response to a parameter of the activity signal, and

means for establishing a pacing rate in response to a combination of said pacing function and the short term variation thereby to produce a smooth transition in pacing rate when exercise is encountered and termination.

14. The method of heart pacing comprising the steps of:

monitoring at least one physiological parameter indicative of the metabolic condition of a patient,

establishing a long term averaged value from said parameter indicative of an individual patient'"'"'s condition,

formulating from said averaged value a primary functional relationship for control of the pacing rate of an individual patient,

deriving an instantaneous physiological change in the patient'"'"'s condition induced by exercise that varies as a function of the patient'"'"'s individual need for variation in pacing rate from said primary functional relationship, and

controlling the pacing rate of the patient in response to a basic pacing control algorithm superimposing dynamic variations in the instantaneous changes upon the primary functional relationship to derive a modified dynamic function of the long term average value.

15. The method of heart pacing comprising the steps of:

monitoring at least one physiological parameter indicative of the metabolic condition of a patient,

establishing a long term function of said monitored parameter indicative of an individual patient'"'"'s condition,

formulating from said long term function a base line pacing control signal,

establishing a dynamic short term signal indicative of a patient'"'"'s metabolic condition,

modifying the base line pacing control signal upward and downward dynamically as a function of said dynamic short term signal to establish a new dynamically varying base line for the pacing control signal, and

controlling the pacing rate of the patient as a function of the base line pacing control signal with the new dynamically varying base line.

16. Apparatus for pacing the heartbeat of a patient, comprising in combination:

measuring means for monitoring at least one physiological parameter indicative of the metabolic condition of a patient,

means for establishing a long term base line function from the monitored parameter,

means for dynamically modifying the base line function upward and downward with short term changes derived from the parameter being monitored,

and means for controlling the pacing rate of the patient from the dynamically modified long term baseline function.